textproduct: Quad Cities

KEY MESSAGES

- Precipitation chances increase late tonight into Sunday. Strong to severe storms remain possible, with the primary focus Sunday evening, and then again Monday afternoon and evening. Additional severe storms are possible on Tuesday as well.

- An active pattern keeps rain chances going through most of next week, but with plenty of dry hours in between. Rainfall amounts may exceed 2" (35-45% chance at any one location) through next Saturday.

- Increasing heat and humidity Sunday and Monday may require heat headlines, but will be dependent on clouds and precipitation. Cooler temperatures are expected later in the week into next weekend with highs likely only in the 70s.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 129 PM CDT Sat Aug 8 2026

Surface high pressure is providing lovely conditions today with lower humidity, plenty of sunshine, and temperatures expected to top out near normal in the lower half of the 80s.

Shortwave energy pushes east into our area late tonight into Sunday which will help kick off showers and storms. Surface winds become southerly as the low level jet strengthens ahead of the wave. CAMs are rather varied in the evolution of convective development late tonight into Sunday morning. NAM3km/FV3/NSSL are suggesting a MCS develops across MN and propagates it southeast into our northern counties by or shortly after 12z. Meanwhile, the HRRR/RRFS suggest primarily elevated convection developing over central IA, that would likely be less organized, and move it through during the morning. While the latter solution seems the slightly more likely outcome, we can't discount the first solution. The overall kinematic and thermodynamic environment would largely suggest a sub-severe threat Sunday morning, with perhaps some hailers being the main threat as mid level lapse rates look to exceed 7C. However, if an organized MCS can sneak into our north then a stronger wind threat may materialize associated with a healthy cold pool.

Depending on how the convection Sunday morning evolves and how quickly we clear out in the afternoon will influence both the severe storm threat later (primarily evening) and how high temperatures/heat index levels reach. LREF probabilities of reaching 100+ heat index readings are in the 30-50% range across our southwest (primarily south of I-80 in IA and southwest of I-74 in IL). There will likely be a rather strong thermal gradient positioned across our area though. Low level convergence may become maximized from WI southwest into parts of our area by late afternoon/early evening, with rapid strom development possible. Effective shear of 35-45 kts in conjunction with MLCAPE of at least 2000-3000 j/kg would support a combination of supercells and linear segments. All severe hazards appear possible, including a few tornadoes, as 0-1km SRH increases to at least 150 m2/s2 after 00z.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 129 PM CDT Sat Aug 8 2026

The upper level flow will remain out of the west-northwest through much of next week, allowing a series of shortwaves to sweep though our region. The low level boundary will reside across our area early in the week, which will keep a more favorable environment in place for severe storms through Tuesday. LREF guidance has the highest probability (40-50%) of surface CAPE exceeding 2000 j/kg along with at least 35 kts of effective shear across our north on Monday before nudging it south on Tuesday. The boundary likely slips to our south by Wednesday and beyond, but remains close enough to keep daily shower and thunderstorm chances in place as additional upper level waves move across. The GFS appears to be an outlier at this time, depicting dry surface high pressure taking control of our weather by next Fri/Sat. Ensemble guidance generally keeps the wetter pattern in place. The LREF probability of receiving at least 2" through next Saturday is around 35-45% across our region.

Temperatures start off the week on the hot side, ranging from the mid 80s to around 90. High humidity levels will also be in place, which may allow heat index readings to exceed 100 on Monday and possibly again on Tuesday (which may require additional heat headlines). Much cooler temperatures are expected during the latter part of the week with the LREF suggesting a 60-90% chance highs remain below 80 by Thursday along and north of I-80 and the entire area by next Fri-Sat.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 620 PM CDT Sat Aug 8 2026

Winds to remain 5 knots or less through 12z/09. After 12z/09 a scattered to broken line of SHRA/TSRA will sweep through eastern Iowa and northern Illinois through 19z/09. Brief MVFR/IFR conditions will be possible in SHRA/TSRA. After 19z/09 a second round of SHRA/TSRA is expected to develop mainly along/east of the Mississippi.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.